In the production of cables, it is usual to measure the eccentricity, that is, the relative position of the conductor in the cable sheath. The eccentric position of the conductor can mean that in a region of the perimeter, the wall thickness of the sheathing does no more provide sufficient insulation. On the other hand, in the production it is aimed to keep the amount of material per unit length at optimum, that means to avoid too high a consumption of material. An eccentricity measurement determines whether there are displacements of the conductor in the sheathing.
Different methods working with and without contact have become known for the eccentricity measurement in cables. It will not be incurred to the same in more detail.
In particular, cables with smaller diameters are produced with considerably high speed, from some meters per second up to 30 m per second, for instance. An eccentricity measurement is performed in measurement intervals of 1 to 2 seconds, for instance. For instance, some hundred measurement values can be generated in one measurement interval with a non-contact measurement method. In the eccentricity measurement, it is known to perform a measurement on plural locations spaced apart across the perimeter direction of the cable at the same time. In this way, it is possible to determine the eccentricity more accurately with respect to amount and direction. Further, it is known to represent the measurement values graphically, such that the machine operator can recognise an eccentricity and can take suitable countermeasures, as the case may be, for instance by adjusting the extruder tool. In the known method, the measurement values of a measurement interval are averaged. In doing so, it has been proven in an optical examination that samples have eccentricities which could not be recognized in the graphic representation.
The present invention is based on the objective to provide a method for visualising measurement values in the eccentricity measurement of cables, which makes an eccentricity visual in a graphical representation even at rapid fluctuations of the eccentricity values.